The point is, that if something is illegal for one party, it's illegal for all. The point isn't that the USSR crimes are ok because Nazi Germany did it, it's that if it is a crime for the USSR then it must be a crime for Nazi Germany, or the UK, or the US.

This, of course, isn't how the world works. But if you believe it should be, it's hard to accept the Russians are the only ones who have crimes to answer for - they just seem to be the only ones being brought to account.